| About 90% of the exploitation of titanium ore is used to produce titanium dioxide every year.Currently,the main process for producing titanium dioxide from ilmenite is sulphate and chloride processes.The sulphate process is so long,the operation requirements are fine and the "three wastes" emissions are large.About the chloride process,which needs high grade raw material,and the technology is difficult and expensive.However,the solvent extraction has the simplified operating procedures and facilities,low operating cost,the extractant recycling is renewable,and there is no polluted source to the external emission.Therefore,the separation and purification of titanium in hydrochloric acid leaching solution by solvent extraction were studied in this paper.First,making the extraction capacity,selectivity,emulsification trend and phase separation performance as the reference standard,meanwhile,taking the stripping rate,water solubility and easy to obtain into consideration.The selection of various extractants was carried out.Finally,a volume fraction of 40% extraction agent as called as i-N218 and 60% diluent was selected as the mixed extractant.After that,the optimum conditions to extract titanium by single stage were as follows: the concentration of hydrogen ion concentration as same as 2# leaching solution,the temperature was 313.15 K,the stirring speed was 400 r/min,and the reaction time was 7 min.Under the optimal conditions,because of competing with each other,the saturated extraction of titanium by extractant was 13.45 g/L,to ron was 97.16 g/L and 2.61 mol/L to hydrogen.In order to increase the extraction rate of titanium more than 99%,a multi-stage countercurrent extraction process was studied.In the process of O/A optimization,the experiment found that the real stages with the extraction rate more than 99% were less than theoretical calculations.When the O/A was 1.5,the real stages were the least and the optimum stages were 4,meanwhile,it was found that hydrochloric acid may had synergistic effect on extracting titanium or i-N218 had the ability to extract titanium.In the process of multistage countercurrent stripping,the optimum conditions were as follows: the concentration of hydrogen ion in the cleaning mixture was 10mol/L and the stage was 1,the concentration of the hydrogen ion in the stripping solution was 4 mol/L,and the stripping stages were 5.Besides,the stripping temperature was 313.15 K,and the O/A was 3:1.The stripping rate of titanium could reach 76.56% by countercurrent stripping and the concentration of titanium inthe stripping solution was 40.55 g/L and the purity was 99.84%.Finally,the mechanism and thermodynamics of all extractions were studied.The extraction coefficient and thermodynamic enthalpy of different extractant to extract titanium,iron and hydrogen were obtained by slope method.The FT-IR was used to analyze the organic phase before and after extraction.It was found that the extraction of hydrochloric acid and titanium mainly due to the effect of hydrogen bond in hydroxy group and the effect was stronger when acted with titanium.The diluent could form a stable complex with the iron.i-N218 extraction of titanium and hydrogen is due to the intermolecular hydrogen bonding between oxygen atoms on the carbonyl group and titanium and hydrogen in hydrochloric acid medium.The carbonyl of i-N218 could form a stable complex with iron and thus had a strong ability to extract it. |
PDF Full Text Request